Prior works have allowed to establish that there is a correlation between the resistance to corrosion in the presence of H.sub.2 S and the hardness of the metal. It has been determined that carbon steels and/or low-alloy steels having a hardness lower than or equal to 22 HRC have a good corrosion strength in the presence of H.sub.2 S. It has therefore been decided to characterize steel by its HRC hardness. The NACE/MR-0175 standard lays down that the carbon steels used in the petroleum field are considered to be compatible with H.sub.2 S if they have a hardness below 22 HRC, the carbon contents being less than or equal to 0.38%. Considering the correspondence between the HRC hardness and the tensile strength Rm, this mode of characterization leads to select steels allowing to obtain products of strength Rm lower than about 800 MPa. It is clear that this can lead to non-optimized armouring wire dimensions. However, the NACE/MR-0175 standard provides for the case of low-alloy, hardened and tempered steels that do not meet the hardness requirement of less than 22 HRC. In this case, these steels must be capable of withstanding corrosion under stress .sigma. in an H.sub.2 S medium (NACE/TM01-77 standard). A test performed on a representative sample will allow to check that steels in this state can be used for the manufacture of metal structures that must withstand the effects of stress corrosion in an H.sub.2 S medium. The stress .sigma..sub.threshold beyond which test TM01-77 is not satisfied also has to be determined. It needs to be known that a test TM01-77 (commonly referred to as SSCC for Sulfide Stress Corrosion Cracking) lasts for about 30 days, which is not comparable to a hardness type characterization test.
A faster method than steel characterization tests TM01-77 is therefore required.